Liquid crystal display devices are characterized by thin profile, light weight and low power consumption, and are widely used in various fields. The display performance thereof has advanced dramatically over the years, and now even surpass CRTs (Cathode Ray Tube).
A display method of a liquid crystal display device is determined depending on how liquid crystals are aligned in a cell. Conventionally known display methods of liquid crystal display devices are, for example, a TN (Twisted Nematic) mode, an MVA (Multi-domain Vertical Alignment) mode, an IPS (In-Plane Switching) mode and an OCB (Optically self-Compensated Birefringence) mode.
Liquid crystal display devices using such display methods have been mass produced. Particularly liquid crystal display devices in a TN mode are widely used by the general public. However liquid crystal display devices in a TN mode require improvement in terms of increasing the response speed and viewing angle.
In the case of an MVA mode, on the other hand, slits are formed in a pixel electrode of an active matrix substrate, and protrusions (ribs) for controlling the alignment of liquid crystal molecules are disposed in a common electrode of a counter substrate, so that fringe fields generated by these slits and ribs disperse the alignment direction of the liquid crystal molecules into a plurality of directions. An MVA mode implements a wide viewing angle by dividing the directions, where liquid crystal molecules tilt down when a voltage is applied, into a plurality of types (multi-domains). Since an MVA mode is a vertical alignment mode, higher contrast can be obtained compared with TN, IPS and OCB modes. However an MVA mode requires improvements in terms of simplifying manufacturing steps, and also in increasing the response speed, just like the case of a TN mode.
To solve the process problems of an MVA mode, a display method (referred to as a “transverse bend alignment” (TBA) mode in this description) for using p-type nematic liquid crystals as a liquid crystal material and driving the p-type nematic liquid crystals using a transverse field has been proposed. In this method, a transverse field is generated by using such an electrode as a comb type electrode, and the alignment direction of the liquid crystal molecules is specified by the transverse field. Since this method is a vertical alignment mode, a high contrast ratio can be implemented.
An example of a liquid crystal display device that has been disclosed includes: a first and second substrates which face each other; a liquid crystal material layer which is injected between the first and second substrates and perpendicularly aligned with respect to the first and second substrates; and at least two or more electrodes which are formed on one of the first and second substrates, and are parallel with each other (e.g. see Patent Document 1).
The TBA method, which does not require alignment control by protrusions, has a simple pixel configuration, and has excellent viewing angle characteristics.    [Patent Document 1] Japanese Kokai Publication H10-333171